Automobile front end alignment equipment

ABSTRACT

Automobile front end alignment equipment in which a platform comprised of a pair of trucks correlated for like orientation while free for universal movement on a horizontal surface, supports respective carriages for free swinging about respective vertical axes, which carriages engagingly support front wheels of a vehicle in predetermined relation to the wheels of a vehicle, and a bracket attachable to a wheel whereby correlated toe-in toe-out and camber of wheels may be simultaneously measured.

ited States Pattern Dick [4 ch. 22, 11972 [54] AUTOMOBILE FRONT END3,411,346 11/1968 Gagliardi ..33/203.13 X ALIGNMENT EQUIPMENT 3,457,6537/1969 Dick 33/203.18 X [72] Inventor: Roy E. Dick, 3758 Blue Rock Road,Cin- P i E i -Willia D M 1ij ,J

cinnati, Ohio 45239 Attorney-Pearce & Schaeperlaus [22] Filed: Aug. 5,1968 A [21] App1.No.: 757,190 [57] ABSTRACT Related Application DamAutomobile front end alignment equipment in which a platform comprisedof a pair of trucks correlated for like orienta- [63]Continuation-impart of Ser- No- 386,460, May tion while free foruniversal movement on a horizontal surface, supports respectivecarriages for free swinging about respective vertical axes, whichcarriages engagingly support front wheels of a vehicle in predeterminedrelation to the wheels of a vehicle, and a bracket attachable to a wheelwhereby correlated toe-in toe-out and camber of wheels may besimultaneously measured.

8 Claims, 12 Drawing Figures [52] U.S.Cl ..33/203.13,33/203.18 [51]Int.Cl. ..G011b7/30 [58] FieldofSearch... ..33/203.12,203.13,203.14

[56] References Cited UNITED STATES PATENTS 2,777,211 1/1957 Martin..33/203.13 3,187,440 6/1965 Merrilletal, 33/2( )3.13

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AtJ'loMomLE rnomr ism) ALIGNMENT EQUIPMENT This application is acontinuationin-part of my copending application Ser. No. 386,460 filedMay 19, 1964.

This invention relates to devices for aligning wheels of an automotivevehicle or the like. In particular, this invention relates to a devicehaving electrically operated gauges which indicate the camber of wheelsand the degree of toe-in or toeout ofthe wheels ofa vehicle.

An object of this invention is to provide a device which can be mountedon a wheel and which, upon adjustment in place on the wheel, indicateson a galvanometet the degree of camber ofthe wheel.

A further object of this invention is to provide such a device in whichan upright column can be attached to a wheel and in which an indicatorarm pivotally connected to the column can be adjustably swung to ahorizontal position and in which swinging of the adjustment arm actuatesa potentiometer to cause registry on a galvanometer of a valuedetermined by the degree of camber ofthe wheel.

A further object of this invention is to provide a device for measuringthe degree of toe-in or out of a vehicle in which the wheels arepositioned on rollers carried by carriages which can swing as the wheelsare rotated and in which a linkage is connected to each carriage foroperating a potentiometer, the reading of the potentiometers beingdetermined by the degree of swinging of the carriage caused by thetoe-in or toe-out of the wheels mounted thereon.

A further object of this invention is to provide such a device in whicheach carriage cooperates with a fork or gear con nected to one of thepotentiometers for swinging or turning the potentiometer to a degreedetermined by the degree of V swinging of the carriage and in which eachpotentiometer is connected to a galvanometer which provides readingsindicating the degree ofswinging ofthe carriage.

A further object of this invention is to provide such a device inwhichthc carriages are mounted on respective trucks which are incooperation with a truck correllating bar and spaceable from one anotherin relation to the vehicle wheel tread spacing.

A further object of this invention is to provide at least one truck withsupporting wheels which permit free shifting in any substantiallyhorizontal direction.

A further object of this invention is to provide on each carriage,roller structure which so cooperates with a vehicle wheel tire thereonthat the carriage and truck are urged to seek location in centrallateral relation beneath said tire.

A further object of this invention is to provide such a device in whichthe galvanometers are located in association on a console forsimultaneously reading and comparison.

A further object ofthis invention is to provide such a device in whichmotor-driven rollers of the carriage cause rotation of the wheels ofthevehicle.

The above and other objects and features of the invention will beapparent to those skilled in the art to which this inven tion pertainsfrom the following detailed description, and the drawings, in which:

FIG. I is a plan view ofa device for determining camber ofa wheel, thedevice being constructed in accordance with an embodiment of thisinvention;

FIG. 2 is a View in side elevation of the device illustrated in FIG. Ipartly broken away and in section to reveal interior constructiorl, analternate position of an actuator arm thereof being indicated indot-dash lines;

FIG. 3 is a fragmentary view in transverse section showing the devicemounted on a wheel ofa vehicle;

FIG. 4 is a view in side elevation taken in the direction of arrow 4 inFIG. 2;

FIG. 5 is a plan view ofa portion of the device for determining thedegree of toe-in or out of wheels; portions of ramps thereof beingomitted, the centerline of the operative position of tires on the wheelsbeing shown in dot-dash lines;

FIG. 6 is a view in vertical section taken on the line 6-6 in FIG. 5,and portions being omitted for clarity;

FIG. tIiA is a view in vertical section taken on the line tiA- oA inFIG. 55;

FIG. '7 is a view in side elevation of a rear wheel support stand;

FIG. 7A is a view in end elevation of the rear wheel support stand shownin FIG. 7;

FIG. b is a view in front elevation of a control console;

FIG. IIA is a view in end elevation of the console of FIG. 8', and

FIG. 9 is a schematic wiring diagram ofthe device.

In the following detailed description and the drawings, like referencecharacters indicate like parts.

In FIGS. I, 2, and I inclusive is illustrated a camber determiningdevice indicated generally at II), which forms a portion ofan alignmentdetermining device constructed in accordance with an embodiment of thisinvention. The device It) includes an upright column or main bracket I2onwhich is mounted a stationary bracket I3 and an extension portion I211carrying a movable bracket I4. The stationary bracket I3 carries a pairof abutment members I6. The movable bracket Id carries a single abutmentmember I7. The movable bracket Id includes a main bar secured toextension portion Ila of the main bracket. An arm I8 is mounted on mainbracket I2 and transverse horizontal shaft IS is journaled therein.Shaft I9 is rotatable by means of crank handle I and carries pinion gear20 in mesh with rack teeth ?;I of extension portion 12a. A lock pawl 22is pivotally mounted on. arm It for use in locking pinion 20 to secureextension portion Ilia against telescoping into main bracket 12. Thecolumn can be mounted in engagement with a front wheel 23 ofa vehicle,as indicated in FIGS. 3 and t, with the ball members 16 and I7 engaginga rim portion 24 of the wheel. A hinge member 26 (FIGS. I and 2) isfixedly attached to the column I2. The column is mounted with the hingemember 26 extending transversely of the wheel and the axis of the hingesubstantially horizontal. An actuator arm 28 is pivotally mounted onhinge pins 29 (FIG. I) carried by the hinge member 26 and can swing fromthe position shown in full lines in FIG. 2 to positions such as the oneshown in dotdash lines in FIG. 2. A potentiometer 34, is mounted in theactuator arm 2d and the stationary fork 27 mounted on the shaft ofpotentiometer 3d cooperates with surface 26:: of member 26. A bubblelevel 32 (FIGS. I and 2) is mounted on the actuator arm 28 so that, asthe actuator arm is swung between the positions illustrated in FIG. 2,the position at which the actuator arm .28 is horizontal can bedetermined from the bubble level 32. The potentiometer 34 mounted onactuator arm 28 rotates about a shaft thereof which is held againstrotation, that is in fixed relation to hinge member 26 by fork 27carried on said shaft, so that, as the actuator arm 28 is swung up ordown, the movable contact of the potentiometer moves along the coilthereof. A galvanometer 36 is connected to the potentiometer 3 i and, asthe movable contact of the potentiometer moves along the coil thereof,the reading of the galvanometer is varied, and the reading of thegalvanometer indicates the degree to which the position of the columnvaries from the vertical, thus indicating the degree of camber of thewheel. The electrical connections between the potentiometer 34 and thegalvanometer 36 will be described in greater detail hereinafter inconnection with the overall electrical circuitry ofthe device.

When the degree of camber of the: wheel has been deter mined with theaid of the camber-determining device It), any adjustments needed in thecamber of the wheel can be made. Then, the camber-determining device canbe temporarily removed from the wheel and used in similar manner inconnection with the second front wheel, and the front wheels then placedin cooperative relation on toe-in alignment platform 4I (shown in FIGS.5, 6, and 6A) and the rear wheels are supported at like elevation as bystands 47 which as shown in FIGS. 7 and 7A may have an upper contoursimilar to that of rollers El, 52, and 53. The platform 41 is comprisedof bar 33 and trucks 39, It) supported on wheels 42, which support theplatform trucks 39, II) in substantially horizontal position. In

such placement of the front wheels, ramps 43 and 44 can be used and aretemporarily attached to the trucks 39, 40 of platform 41 by means ofpins 46. The pins 46 extend through integral portions of the ramps, andare received in upright bores 48 (FIG. in the trucks 41. The ramps canguide wheels ofa vehicle into position on mechanism carried by thetrucks 39, on which tires 49 of the vehicle are shown in FIGS. 6 and 6A.The trucks 39, 40 and the mechanism carried thereby are in large degreeduplicates and like reference characters will be applied to like partsthereof. When the wheels ofa vehicle are in the position shown in FIGS.6 and 6A, each tie is disposed on rollers 51, 52, and 53 (FIGS. 5, 6,and 6A). The rollers 51, 52, and 53 are mounted on a swinging carriage50 which in turn is mounted on a respective one of trucks 39, 40 forswinging about a substantially vertical axis 79.

Roller 51 is journaled on bearings 54 mounted on shaft 55 which is inturn supported by carriage 50 to which it is fixed adjacent its ends bypins or set screws 56. Roller 51 is centered on shaft 55 between sideflanges 57, 58 of carriage 50.

Roller 53 comprises a cylindrical central portion 59 mounted in bearings60 mounted on shaft 61 which is in turn supported by carriage 50 towhich it is fixed adjacent'its ends by pins or setscrews 62. Thecylindrical central roller portion 59 is mounted on shaft 61 in centeredrelation between side flanges 57, 58 of carriage 50. Laterally ofcylindrical central roller portion 59', a pair of frustoconic rollerportions 63 are mounted by bearings 64 for rotation on shaft 61. Asshown the small diameter ends of roller portions 63 are adjacent rollerportion 59. Compression springs 65 are provided annularly of shaft 61between frustoconic roller portions 63 and carriage side flanges 57, 58to urge roller portions 63 toward roller portions 59. A thrust bearing,not shown, may be provided between springs 65 and roller 63 to reducefrictional drag and wear. Thus roller portions 59 and 63 may rotate onshaft 61 at different speeds depending upon their engagement with adriving member such as tire 49.

Roller 52 comprises a cylindrical central roller portion 66 mounted bymeans such as set screws 67 in fixed relation to shaft 68 for rotationtherewith and of a width slightly shorter than the transverse width ofthe tire treads which will cooperate therewith. Roller portion 66, somounted, is centered between carriage side flanges 57, 58. As shown inFIG. 5, side flanges 57, 58 may have integral boss portions 69 andsupport journal bearings 70 for shaft 68. Laterally of cylindricalcentral roller portion 66, a pair of frustoconic roller portions 71 aremounted by bearings 72, for rotation on shaft 68. The small diameterends of roller portions 71 are adjacent roller portion 66. Compressionsprings 73 are provided annularly of shaft 68 between frustoconic rollerportions 71 and carriage side flanges 57, 58 to urge roller portions 71toward roller portion 66. A thrust bearing, not shown, may be providedbetween spring 73 and roller 71 to reduce frictional drag and wear. Thusfrustoconic roller portions 71 may rotate relative to shaft 68 andcentral roller portion 66 at speeds dependent upon their engagement witha driving member such as tire 49.

Shaft 68, journaled for rotation in bearings 70 is thus supported bycarriage 50.

A motor 74 having an angle drive speed reduction gear box 75, is mountedon carriage 50 with its output shaft 75a in driving relation to shaft 68such that cylindrical central roller portion 66 may by operation ofmotor 74 apply driving power to tire 49 to rotate-same.

As shown in FIGS. 6 and 6A, carriages 50 each have a central hub boss 76through which retaining bolt 77 extends and annularly of which a taperedroller bearing 78 supports carriage 50 for rotation about the centralvertical axis 79. An additional thrust bearing 80 is provided annularlyof hub boss 76 to support the carriage adjacent the periphery thereof.Bolt 77 in cooperation with nut 77a (and suitable washers and the likenot shown) provide initial load on the bearings 78, 80 and precludeseparation ofthe carriage from the truck.

Each truck 39 and 40 is provided with means for easy rolling movement inany direction over surface 45 which as shown may be a plurality ofsupporting casters 81, which as shown are preferably of a type whichreadily roll in any, direction and thus facilitate movement of the truckin any direction. The axis about which the casters shown swivel, lies ina plane between the dual wheels 42 thereof and is coincident with theaxis of the caster shank or tank 83.

Means are provided for retaining the trucks 39, 40 in abreast relationwhile permitting them to seek spacing related to the tread spacing ofthe wheels 49 supported on carriages 50. As shown truck 40 has a pair ofprojecting arms 84 in which bar 38 is secured in fixed relation andextending horizontally perpendicular to the centerline 85 of truck 40.Truck 39 has a pair of arms 86 in which low friction bearings 87 areprovided. Bar 38 is received in cooperative relation to bearings 87 suchthat truck 39 may move freely toward and away from truck 40 while thetruck centerlines 88 and 85 remain parallel. The swinging carriages 50are supported on bearings 78, 80 so that the carriages can swing freelyof the pivots thereof, However, swingable lock dogs 89 are provided forlocking the carriages by clockwise swing of the dog from the positionshown in FIG. 6 into notch 90. The swinging carriages 50 may thus belocked in centered position, the trucks shifted as needed to place thecarriage to receive the wheel before the wheels are moved into positionon the rollers thereof.

When the wheels have been mounted on the rollers 51, 52, and 53, thedogs 89 are released and through operation of motors 74 the rollers andwheels are rotated in unison. As the wheels 49 rotate, driven by rollerportions 66 in cooperative engagement with the tire treads, thefrustoconic faces of the roller portions 63, 71 engage the side walls ofthe tire outboard of the tread and urge the tire to center on rollerportions 51, 66, and 59. Such centering of the tire will urge the trucks39, 40 to spaced relation such that the spacing of the center line ofthe tire treads will substantially equal the spacing of the centerlinesof the respective trucks. Simultaneously the carriages 50, free torotate about their axes 79, swing into ositions in which theircenterlines respectively coincide with the centerline of the respectiveengaging tire tread.

Each truck-carriage assembly has means for sensing and communicating therelative position of axial rotation of the carriage to the truck. Eachtruck, as shown, has a protective housing 91 in which a potentiometer 92is mounted in fixed relation to the truck with its shaft 93 vertical. Afork 94 mounted on shaft 93 has a pair of horizontal arms 95 (FIG. 5)between which finger or roller 96 projects. Finger or roller 96 projectsradially horizontally from carriage 50, as illustrated in FIGS. 5 and 6,into contact 93' with arms 95.

As the rollers 66 are rotated to turn the vehicle wheels, the swingingcarriage 50 can swing from the neutral position shown in full lines to aposition such as that indicated in dotdash lines at 85a, 88a, theamplitude of swinging being determined by the degree of toe-in ortoe-out of the tires 49. As the swinging carriage 50 swings, angularrotation of carriage 50 about axis 79 thus results in related rotationof potentiometer shaft 93, which extends into and operates a movablecontact of potentiometer 92. As shown in FIG. 9, the potentiometer 92 isconnected to a galvanometer 108 in such a manner that the reading ofthegalvanometer 108 indicates the degree to which the movable contact ofthe potentiometer is displaced incident to the swinging of carriage 50of truck 39 (FIG. 5). Similarly, a potentiometer 92 on truck 40 isoperated by carriage 50 on truck 40. The potentiometer 92' is connectedto a galvanometer (FIG. 9), and the reading of the galvanometer 115indicates the degree of displacement of the movable contact of thepotentiometer 92' incident to swinging ofthe swinging carriage 50 oftruck 40 (FIG. 5). Carriage 50 may have provision for mounting offmgeror roller 96 in a plurality of predetermined stations corresponding topositions which wheels assume when turned for steering the vehicle. Asshown in FIG. 8, the galvanometers 36, 108, 115 and motor switch 118421are mounted in console 32 and may have associated pilot lights 35, 107,114, 120 for indicating when the respective circuits are energized. Thecircuits containing galvanometers 36, 108, 115 respectively may becontrolled by switches 35, 109, and 110.

The electric circuitry ofthe device is shown in FIG. 9. Electric poweris supplied through power leads 116 and 117. Operation of the drivemotors 74 is initiated by closing of a motor switch 118 which energizesmotor starting relays 119 (of which one is shown). The motors can bestopped by opening a motor stop switch 121.

Power for galvanometers and potentiometers is supplied through atransformer 122 and a rectifier 123 which supplies unidirectionalcurrent of appro riate voltage across leads 124 and 126. Coils of thepotentiometers 34, 92 and 92 are connected across the leads 124- and126. One lead of the gal vanometer 36 is attached to a line 127 which isconnected to the leads 124 and 126 through equal voltage dividingresistors 128 and 129, respectively, so that the line 127 is at apotential midway between the voltages of the leads 12- 1 and 126. Themovable contact of the potentiometer 34 is connected to the other sideofthe galvanometer 36 so that the galvanometer 36 has a zero readingwhen the movable contact of the potentiometer 34 is centered on the coilthereof, and displacement of the movable contact in opposite directionscauses deflection of the indicator of the galvanometer 36 in oppositedirections. In a similar manner, one lead of the galvanometer 108 isconnected between voltage dividing resistors 131 and 132 connected tothe leads 124 and 126 respectively, and the other lead of thegalvanometer 108 is connected to the movable contact of thepotentiometer 92. The galvanometer 115 is similarly connected betweenvoltage dividing resistors 133 and 134 which are connected to the leads124 and 126, respectively, and to the movable contact of thepotentiometer 92. Thus, each galvanometer registers the degree to whichthe movable contact of the potentiometer associated therewith isdisplaced from a zero reading. From the galvanometer 36 is determinedthe degree of the camber of a wheel. If desired a second camberdetermining device 111 with a respective galvanometer 36 can also beused to obtain simultaneous determination of camber of a second wheel.From the galvanometers 108 and 115 is determined the degree of toe-in ortoe-out of the wheels, and from these readings can be determined thedegree and type of adjustments required to correct alignment ofthewheels.

Cable 100 provides electrical connection between the power source andconsole 32, while console 32 and motors 7 1, potentiometers 34, 92 and92' are respectively provided by cables 101, 102, 103 and 104.

The alignment indicating device illustrated in the drawings anddescribed above is subject to structural modification without departingfrom the spirit and scope of the appended claims.

Having described my invention, what I claim as new and desire to secureby letters patent is:

1. A device for indicating alignment of wheels ofa vehicle when engagingonly the treads of said wheels which comprises a platform including twotrucks coupled by means retaining the trucks against change in relativeorientation while permitting translatory movement of at least one trucktoward and away from the other truck, a pair ofcarriages mounted on saidpair of platform trucks for swinging in substantially horizontal planes,a pair of rollers rotatably mounted on each carriage for supportingtires and wheels of the vehicle, a third roller rotatably mounted oneach carriage and flanged to cooperate with the tread face and edges ofa tire to center same on the carriage and thereby cause the platformtrucks to assume a spacing related to the spacing of the vehicle wheelssupported on the carriages, means for unisonly rotating one of therollers on each carriage for rotating the vehicle wheels thereon, apotentiometer connected to each carriage, a movable contact of eachpotentiometer being displaceable to a degree determined by the swing ofthe carriage associated therewith and a galvanometer connected to eachpotentiometer to register the degree of displacement of the movablecontact thereof for indicating the swinging ofthe carriage associatedtherewith.

2. A device for indicating alignment of wheels of a vehicle whenengaging only the treads of said wheels which comprises a platformincluding at least one truck coupled to means retaining the truckagainst change in relative orientation while permitting translatorylateral movement of said truck, a carriage mounted on said truck forswinging in a substantially horizontal plane, a pair of rollersrotatably mounted on said carriage for supporting a tire and wheel ofthe vehicle, a third roller rotatably mounted on said carriage andflanged to cooperate with the tread face and edges of a tire to centersame on the carriage and thereby cause the truck by lateral movement toassume a position related to the location of the vehicle wheel supportedon the carriage, means for rotating one of the rollers on said carriagefor rotating the vehicle wheel thereon, a potentiometer connected tosaid carriage, a movable contact of said potentiometer beingdisplaceable to a degree determined by the swing of the carriage and agalvanometer connected to said potentiometer to register the degree ofdisplacement of the movable contact thereof for indicating the swing ofthe carriage.

3. A device for indicating alignment of wheels of a vehicle whenengaging only the treads of said wheels which comprises a platformincluding one truck coupled to means retaining the truck against changein relative orientation while permitting translatory lateral movement ofsaid truck, a carriage mounted on said truck for swinging in a.substantially horizontal plane, a pair of rollers rotatably mounted onsaid carriage for supporting a tire and wheel of the vehicle, a thirdroller rotatably mounted on said carriage and flanged to cooperate withthe tread face and edges of a tire to center same on the carriage andthereby cause the truck by lateral movement to assume a position relatedto the location of the vehicle wheel supported on the carriage, a secondpair of rollers rotatably mounted for supporting a second tire and wheelrelative to said platform, a third roller rotatably mounted forcooperation with a tire supported on said second pair of rollers andflanged to cooperate with the tread face and edges of a tire to centersame on the second pair of rollers, means for unisonly rotating one ofeach of said pairs of rollers for rotating the vehicle wheels thereon, apotentiometer connected to said carriage, a movable contact of saidpotentiometer being displaceable to a degree determined by the swing ofthe carriage and a galvanometer connected to said potentiometer toregister the degree of displacement of the movable contact thereof forindicating the swing of the carriage.

4. A device for indicating alignment of wheels of a vehicle whenengaging only the treads of said wheels which comprises a platformincluding two trucks coupled by means retaining the trucks againstchange in relative orientation while permitting translatory movement ofat least one truck toward and away from the other truck, a pair ofcarriages mounted on said pair of platform trucks for swinging in asubstantially horizontal plane, a pair of rollers rotatably mounted oneach carriage for supporting tires and wheels of the vehicle, a thirdroller rotatably mounted on each carriage and flanged to cooperate withthe tread face and edges of a tire to center same on the carriage andthereby cause the platform trucks to assume a spacing related to thespacing of the vehicle wheels supported on the carriages, means forunisonly rotating one of the rollers on each carriage for rotating thevehicle wheels thereon, a potentiometer connected to each carriage, amovable contact of each potentiometer being displaceable to a degreedetermined by the swing of the carriage associated therewith andgalvanometer means connected to the potentiometers to register thedegree of displacement of the movable contacts thereof for indicatingthe swing of the carriages associated therewith.

5. in a device for indicating alignment of wheels of a vehicle whenengaging only the treads of said wheels which comprises a pair of truckscorrellated in abreast spaced relation by means permitting the truckspacing to change to form a platform, a pair of carriages, one carriagebeing mounted on each truck for swinging about a vertical axis, aplurality of parallel rollers on each carriage for supporting tires andwheels of the vehicle, means for simultaneously rotating one of therollers on each carriage for rotating the vehicle wheels thereon, meanscooperating with the tires outboard of the treads thereof to orient thecarriage so the centerline of the tire tread extends transversely of theparallel rollers in engagement therewith, a potentiometer connected toeach carriage, a movable contact of each potentiometer beingdisplaceable to a degree determined by the swing of the carriageassociated therewith, and a galvanometer connected to each potentiometerto register the displacement of the movable contact for indicating theswinging of the carriage associated therewith.

6. A device in accordance with claim characterized by the fact that eachtruck is supported for universal horizontal movement so they will moveto positions in which the carriages are supported beneath and in alignedassociation with the wheels.

7. A device in accordance with claim 5 in which the means cooperatingwith the tires outboard of the treads thereof comprise a pair offrustoconic rollers journaled for free rotation on said carriage andabout a horizontal first axis, a second pair of frustoconic rollersjournaled for free rotation on said carriage V and about a horizontalaxis parallel to the axes of said plurality of parallel rollers and tothe horizontal first axis from which it is spaced, the frustoconic facesof one of each pair of frustoconic rollers engaging the tire to one sideof the tread and the other frustoconic rollers engaging the tire to theother side of the tread, means urging said pairs of frustoconic rollersto assume positions symmetric about a predetermined line extendingtransversely of the plurality of parallel rollers.

8. A device in accordance with claim 7 characterized by the fact thatthe said horizontal first axis intersects the vertical axis about whichthe carriage swings.

1. A device for indicating alignment of wheels of a vehicle whenengaging only the treads of said wheels which comprises a platformincluding two trucks coupled by means retaining the trucks againstchange in relative orientation while permitting translatory movement ofat least one truck toward and away from the other truck, a pair ofcarriages mounted on said pair of platform trucks for swinging insubstantially horizontal planes, a pair of rollers rotatably mounted oneach carriage for supporting tires and wheels of the vehicle, a thirdroller rotatably mounted on each carriage and flanged to cooperate withthe tread face and edges of a tire to center same on the carriage andthereby cause the platform trucks to assume a spacing related to thespacing of the vehicle wheels supported on the carriages, means forunisonly rotating one of the rollers on each carriage for rotating thevehicle wheels thereon, a potentiometer connected to each carriage, amovable contact of each potentiometer being displaceable to a degreedetermined by the swing of the carriage associated therewith and agalvanometer connected to each potentiometer to register the degree ofdisplacement of the movable contact thereof for indicating the swingingof the carriage associated therewith.
 2. A device for indicatingalignment of wheels of a vehicle when engaging only the treads of saidwheels which comprises a platform including at least one truck coupledto means retaining the truck against change in relative orientationwhile permitting translatory lateral movement of said truck, a carriagemounted on said truck for swinging in a substantially horizontal plane,a pair of rollers rotatably mounted on said carriage for supporting atire and wheel of the vehicle, a third roller rotatably mounted on saidcarriage and flanged to cooperate with the tread face and edges of atire to center same on the carriage and thereby cause the truck bylateral movement to assume a position related to the location of thevehicle wheel supported on the carriage, means for rotating one of therollers on said carriage for rotating the vehicle wheel thereon, apotentiometer connected to said carriage, a movable contact of saidpotentiometer being displaceable to a degree determined by the swing ofthe carriage and a galvanometer connected to said potentiometer toregister the degree of displacement of the movable contact thereof forindicating the swing of the carriage.
 3. A device for indicatingalignment of wheels of a vehicle when engaging only the treads of saidwheels which comprises a platform including one truck coupled to meansretaining the truck against change in relative orientation whilepermitting translatory lateral movement of said truck, a carriagemounted on said truck for swinging in a substantially horizontal plane,a pair of rollers rotatably mounted on said carriage for supporting atire and wheel of the vehicle, a third roller rotatably mounted on saidcarriage and flanged to cooperate with the tread face and edges of atire to center same on the carriage and thereby cause the truck bylateral movement to assume a position related to the location of thevehicle wheel supported on the carriage, a second pair of rollersrotatably mounted for supporting a second tire and wheel relative tosaid platform, a third roller rotatably mounted for cooperation with atire supported on said second pair of rollers and flanged to cooperatewith the tread face and edges of a tire to center same on the secondpair of rollers, means for unisonly rotating one of each of said pairsof rollers for rotating the vehicle wheels thereon, a potentiometerconnected to said carriage, a movable contact of said potentiometerbeing displaceable to a degree determined by the swing of the carriageand a galvanometer connected to said potentiometer to register thedegree of displacement of the movable contact thereof for indicating theswing of the carriage.
 4. A device for indicating alignment of wheels ofa vehicle when engaging only the treads of said wheels which comprises aplatform including two trucks coupled by means retaining the trucksagainst change in relative orientation while permitting translatorymovement of at least one truck toward and away from the other truck, apair of carriages mounted on said pair of platform trucks for swingingin a substantially horizontal plane, a pair of rollers rotatably mountedon each carriage for supporting tires and wheels of the vehicle, a thirdroller rotatably mounted on each carriage and flanged to cooperate withthe tread face and edges of a tire to center same on the carriage andthereby cause the platform trucks to assume a spacing related to thespacing of the vehicle wheels supported on the carriages, means forunisonly rotating one of the rollers on each carriage for rotating thevehicle wheels thereon, a potentiometer connected to each carriage, amovable contact of each potentiometer being displaceable to a degreedetermined by the swing of the carriage associated therewith andgalvanometer means connected to the potentiometers to register thedegree of displacement of the movable contacts thereof for indicatingthe swing of the carriages associated therewith.
 5. In a device forindicating alignment of wheels of a vehicle when engaging only thetreads of said wheels which comprises a pair of trucks correllated inabreast spaced relation by means permitting the truck spacing to changeto form a platform, a pair of carriages, one carriage being mounted oneach truck for swinging about a vertical axis, a plurality of parallelrollers on each carriage for supporting tires and wheels of the vehicle,means for simultaneously rotating one of the rollers on each carriagefor rotating the vehicle wheels thereon, means cooperating with thetires outboard of the treads thereof to orient the carriage so thecenterline of the tire tread extends transversely of the parallelrollers in engagement therewith, a potentiometer connected to eachcarriage, a movable contact of each potentiometer being displaceable toa degree determined by the swing of the carriage associated therewith,and a galvanometer connected to each potentiometer to register thedisplacement of the movable contact for indicating the swinging of thecarriage associated therewith.
 6. A device in accordance with claim 5characterized by the fact that each truck is supported for universalhorizontal movement so they will move to positions in which thecarriages are supported beneath and in aligned association with thewheels.
 7. A device in accordance with claim 5 in which the meanscooperating with the tires outboard of the treads thereof comprise apair of frustoconic rollers journaled for free rotation on said carriageand about a horizontal first axis, a second pair of frustoconic rollersjournaled for free rotation on said carriage and about a horizontal axisparallel to the axes of said pluRality of parallel rollers and to thehorizontal first axis from which it is spaced, the frustoconic faces ofone of each pair of frustoconic rollers engaging the tire to one side ofthe tread and the other frustoconic rollers engaging the tire to theother side of the tread, means urging said pairs of frustoconic rollersto assume positions symmetric about a predetermined line extendingtransversely of the plurality of parallel rollers.
 8. A device inaccordance with claim 7 characterized by the fact that the saidhorizontal first axis intersects the vertical axis about which thecarriage swings.